1. Field of the Invention
The invention is directed to fuel injection valves, and particularly to such a valve for internal combustion engines.
2. Brief Description of the Prior Art
One prior art fuel injection valve, known from German Published, Nonexamined Patent Application DE 196 45 900 A1 employs a pistonlike valve member that is movable axially counter to the force of a closing spring disposed in a bore. The valve member is guided in the bore in a portion remote from the combustion chamber and, toward the combustion chamber, changes into a closing head that is guided in a slide bore which is embodied as a blind bore. On the wall of the slide portion of the bore, there are a plurality of axially offset injection openings, which in the closed state of the valve member are covered by the closing head. By the fuel pressure on the pressure shoulder disposed in the pressure chamber, the valve member is lifted from the valve seat, and as a result the pressure chamber communicates with the lower pressure chamber via a transverse bore and a middle bore embodied in the valve member. The control edge of the closing head, in the opening stroke motion, opens the injection openings in succession, and as a result over the increasing entire injection cross section, a shaping of the course of injection is achieved. When the stroke stop face reaches the stop face embodied in the valve body, the opening stroke is concluded.
In such an injection valve, all the injection openings are opened in the opening stroke motion. In the partial-load range of the engine, the injection quantity is reduced compared to full load, which in this injection valve means on the one hand that the injection pressure is reduced and on the other that the opening time of the injection valve is shortened. Neither of these aspects is optimal with regard to either optimal atomization and distribution of the fuel in the combustion chamber or low exhaust emissions.
The fuel injection valve of the invention for internal combustion engines, has the advantage over the prior art that the opening stroke can be limited by the hydraulically controlled control piston to a portion of the maximum stroke, and as a result only some of the injection openings, or only a partial cross section of the injection openings, is opened.
One embodiment of the invention has the advantage that the maximum stroke can be changed in a simple way, by replacing the relatively readily accessible control piston with another of a different height.
Because of the multi-part construction of the control piston in one embodiment, easy installation of the fuel injection valve is obtained. Depending on the needs for the design of the fuel injection valve, the restoring spring can engage either the hydraulic piston or the thrust rod, which makes it possible to use the stroke stop, which according to the invention is hydraulically variable, in various fuel injection valves. A further embodiment has the advantage that the injection cross section can be reduced by providing that the injection opening is opened only in part.
In another embodiment, the fuel injection valve has the advantage that the control line communicates with a high-pressure collection chamber via a control valve, so that no additional high-pressure fuel source is required for the control pressure in the control chamber.
In a further embodiment, it is advantageously possible to relieve the control line to the fuel tank within a very brief time and thus put the control piston into the first stroke position. It is accordingly possible to change very quickly between the partial stroke and the maximum stroke of the valve member.